Captive screws or captive panel fasteners are well known in the industry. This type of fastener is arranged so that a screw is held in position extending through an opening in a panel, with the threaded end of the screw extending out the other side of the panel. When large panels with many fasteners are used, for example, in aircraft asesmblies, it is important that these fasteners be properly held in position, with the fastener held captive on the panel ready for the securing of the threaded end of the fastener to a nut or into a tapped hole.
One way in which screws have previously been held in position extending through openings in a panel has been through the use of a slotted sleeve with a tapered outer or lower end, and a flange which underlies the head, at the upper end of the sleeve. Immediately behind the tapered end of the sleeve, is a shoulder, so that the screw, with the sleeve attached, may be forced through the hole in the panel, and then, hopefully, the lower end of the sleeve will spring back into its expanded state with the shoulder extending over the remote edge of the hole to hold the fastener onto the panel.
Captive screws of the type described in the preceding paragraph are not entirely satisfactory for a number of reasons. First, the sleeve, which is made of aluminum must be formed of a special type of resilient heat treated aluminum, or it may undergo a "set" so that it will not expand and properly engage the panel after insertion through the panel. In addition, the slotted sleeve must be fairly loose, to permit contraction as the tapered portion of the sleeve is forced through the hole in the panel, and this looseness may reduce the shear load capability of the fastener. It is further noted that the prior fastener as described above normally requires that the fasteners be pounded into the panel so that there is a rapid flexing of the aluminum sleeve, to avoid a "set" and to insure securing of the sleeve in the panel hole. Certain problems have also been encountered with the prior fasteners as described above, in that the retention is not very good, and even laying the panel on a table may cause some of the fasteners to pop out from the panel. In addition, special preparation or chamfering of the input hole in the panel is recommended for use in connection with captive screws of the type mentioned above.
Accordingly, a principal object of the present invention is to avoid the problems of prior types of captive screws or panel fasteners as described hereinabove.